Field of the Invention
The present invention relates to magnetic resonance imaging (MRI), and more particularly, to methods and systems for sub-nanometer magnetic resonance imaging.
Brief Description of the Related Art
Magnetic resonance imaging (MRI) has revolutionized biomedical science by providing non-invasive, three-dimensional biological imaging. See, Mansfield, P. “Snapshot magnetic resonance imaging (Nobel lecture),” Angew Chem Int Ed Engl. 2004; 43:5456-5464. However, spatial resolution in conventional MRI systems is limited to tens of microns, which is insufficient for imaging on molecular and atomic scales. See, P. Glover and P. Mansfield, “Limits to magnetic resonance microscopy,” Rep. Prog. Phys. 65, 1489 (2002).
Atomic-scale magnetic resonance imaging (MRI) would have wide-ranging applications including determining the structure of individual biomolecules, imaging the dynamics of bottom-up molecular engineering, and achieving site-resolved readout in solid-state quantum simulators. See, P. Hemmer, Science 339, 529 (2013); C. A. Palma and P. Samori, Nat. Chem. 3, 431 (2011) J. Cai, et al., Nat. Phys. 9, 168 (2013). Performing conventional MRI on sub-micron length scales, however, is not possible with present systems and methods because macroscopically generated magnetic-field gradients limit spatial resolution, and inductive detection schemes suffer from significant thermal noise.
Great progress has been made using scanning-probe-based magnetic gradient techniques, which enable nanoscale MRI using ultrasensitive force detection at cryogenic temperatures or fluorescence measurements of optically ‘bright’ spins such as nitrogen vacancy (NV) color centers in diamond.” See, J. A. Sidles, et al., “Magnetic resonance force microscopy,” Rev. Mod. Phys. 67, 249 (1995); G. Balasubramanian, I. Y. Chan, R. Kolesov, M. Al-Hmoud, J. Tisler, C. Shin, C. Kim, A. Wojcik, P. R. Hemmer, A. Krueger, T. Hanke, A. Leitenstorfer, R. Bratschitsch, F. Jelezko, and J. Wrachtrup, Nature 455, 648 (2008); C. L. Degen, M. Poggio, H. J. Mamin, C. T. Rettner, and D. Rugar, Proc. Nat. Acad. Sci. 106, 1313 (2009); D. Rugar, R. Budakian, H. J. Mamin, and B. W. Chui, Nature 430, 329 (2004); M. S. Grinolds, P. Maletinsky, S. Hong, M. D. Lukin, R. L. Walsworth, and A. Yacoby, Nat. Phys. 7, 687 (2011). However for most MRI applications, measurements must be taken near room temperature, and nearly all targets of interest contain optically ‘dark’ spins that are unpolarized or weakly polarized.